I've seen this come up in locked topics that never actually stated the fix.. I recently created a forum for a group of people in an online game. I asked them that they register with their ingame names to avoid confusion. Multiple users have received the message: "Sorry, but this username has already been taken." when trying to register. I've checked the member lists (all of two people) as well as the word/username censoring and the names they are attempting to register are not listed. One of the usernames that was "taken" was as simple as "Jane". I haven't found a way around it other than telling them to register with different names. Is there a hidden word/username blacklist that is blocking these accounts? Thanks in advance!

Hi, I'm not sure what is the problem but try this: Administration Panel => General => Forum => Security => => Security Administration => Unauthorize subscriptions made with the most commonly used spam usernames.

That was it! Thank you so much!

Glad I could help.